SINGAPORE - With mega-rich Manchester City ready to break the bank once again to fill a Pablo Zabaleta-sized hole at right-back, Tottenham Hotspur's Kyle Walker looks set to become the world's most expensive defender as City aim to sign him for £50 million (S$89.1 million) with an additional £3 million of add-ons.

Here are the current five most expensive defenders of all time in world football.

1. David Luiz, £50 million, from Chelsea to Paris Saint-Germain, 2014

After playing 143 times for Chelsea and winning the Champions League in 2012 during his first spell at the club, PSG came calling and made him the most expensive defender in history. He has since returned to Chelsea and won the Premier League earlier in the year. He also has 56 caps for Brazil.

2. John Stones, £47.5 million, from Everton to Manchester City, 2016

Ahead of his first season of English Football, Manchester City manager Pep Guardiola decided to go big on Stones after the Englishman impressed at Everton. Still only 23, the centre-back has 18 caps for England.

3. Eliaquim Mangala, £42 million, from Porto to Manchester City, 2014

Brought in with high expectations, the Frenchman disappointed after a poor couple of seasons at the Etihad Stadium, was loaned out to Spanish side Valencia for the 2016-17 season. The 26-year-old has eight caps for France.

4. Shkodran Mustafi, £35 million, from Valencia to Arsenal, 2016

A World Cup winner with Germany in 2014, Mustafi was bought by Arsene Wenger to bolster Arsenal's back line ahead of the 2016-17 season. He has since established himself as the Gunners' first-choice centre-back. The German has 19 caps for his country.

5. Nicolas Otamendi, £34m, from Valencia to Manchester City, 2015

Another Manchester City purchase, the Argentinian was bought by then City manager Manuel Pellegrini in the transfer window that also saw the additions of Raheem Sterling, Fabian Delph and Kevin de Bruyne. Otamendi has 44 caps for Argentina.